FIG. 16A is a diagram showing an example configuration of a closed-type speaker 70 according to a conventional technique. The speaker 70 shown in FIG. 16A has a configuration in which a circular magnet 73 and a circular plate 74 are arranged on a back plate 71 such that they surround a center pole 72 provided to the plate 71. The neck portion of frame 75 is fixed to the front face of the circular plate 74. The inner circumferential face of the circular plate 74 and the outer circumferential face of the center pole 72 form a gap, i.e., a magnetic gap GP1, which houses a portion of a voice coil bobbin 76 around which a coil 77 is wound. The neck portion of a vibrating sheet 78 is bonded to a portion of the outer circumferential face of the voice coil bobbin 76 at a position slightly shifted from the end of the outer circumferential face of the voice coil bobbin 76. Furthermore, a circumferential edge of a cap 79 is bonded to the front face (sound emission plane) of the vibrating sheet 78 at a position slightly shifted toward the outer side from the neck portion of the vibrating sheet 78. Furthermore, the vibrating sheet 78 and the voice coil bobbin 76 are arranged such that they are surrounded by the inner circumferential face of the frame 75. Moreover, a damper 80 is provided between the outer circumferential face of the bobbin 76 and the inner circumferential face of the frame 75. The configuration of such a type of speaker is disclosed in Patent document 1, for example.